Like I’ve said before, when you’re a sex educator, there are some questions that you come to expect. There’s not a single classroom of middle schoolers that hasn’t asked me about the origin of HIV.
Zoonosis is when a virus passes between species, and the strongest, most widely-believed theory is that SIV (Simian Immunodeficiency Virus) in monkeys became HIV in humans, probably through monkey-to-hunter transmission. Another, more recent example of zoonosis is Avian Influenza, better known as the bird flu. Remember the H1N1 vaccination public health officials were urging us to get? Animals and humans carry around lots of viruses and bacteria that do them no harm, but when transferred to another species, can have a serious impact – think tapeworms, plague, Lyme disease, rabies, etc.
I strongly encourage you to go to one of my favorite websites for HIV information, Avert.org. Avert does a really great job of discussing all of the HIV origin theories as well as a providing a history and timeline of HIV discoveries.